Abstract. Poly(butylene succinate) (PBSu), poly(2-methyl-1,3-propylene succinate) (PMPSu), and PBSu-rich copolyesters were synthesized using an effective catalyst, titanium tetraisopropoxide. Measurements of intrinsic viscosity (1.20-1.28 dl/g) and gel permeation chromatography demonstrated the success of the preparation of polyesters with high molecular weights. The compositions of the copolyesters were determined in three approaches from 1 H and 13 C NMR (nuclear magnetic resonance) analyses, and good agreement between the results was obtained. The distributions of the comonomers were found to be random from the spectra of carbonyl carbon. Their thermal properties were elucidated using a differential scanning calorimeter and a thermogravimetric analyzer. No marked difference exists among the thermal stabilities of these polyesters. However, the window between the glass transition and the melting temperatures becomes narrower with the increase in the concentration of 2-methyl-1,3-propylene succinate in the copolymers. Additionally, the cold crystallization ability decreases considerably. Finally, PMPSu is an amorphous homopolymer. Wide-angle X-ray diffractograms of isothermally crystallized copolyesters also follow the same trend.